1. Field of the Invention
The present invention relates to a system for controlling X-ray doses when imaging a portion of a patient's anatomy and, in particular, to a system and method for controlling X-ray exposure so as to achieve desired clarity in an X-ray image while minimizing the amount of radiation to which the patient is exposed.
2. The Background Art
The use of X-ray machines for imaging internal portions of a patient's anatomy has become wide spread due to the significant amount of useful information which can be provided. Fractures, sprains and abnormal circulatory conditions can all be diagnosed with little inconvenience to the patient by imaging the internal anatomy in question.
Unfortunately, X-ray diagnostic equipment has a serious draw-back which is of particular concern to patients receiving frequent X-rays. The radiation used to penetrate the anatomy and form the image is known to cause medical problems, such as cancer, if protective measures are not taken. For patients suffering from condition which require frequent imaging, the risks raised by repeated exposure to the X-ray radiation causes significant concerns.
While minimizing the patient's exposure to radiation is important, it is equally important to provide sufficient radiation to allow clear imaging of the internal features of the relevant body part. The accurate determination and setting of X-ray dose (Commonly referred to as technique), is difficult, however, due to the different densities of body parts. Thus, it is challenging to provide the correct X-ray technique, so as to give the best possible image, while simultaneously subjecting the patient to the least amount of radiation.
To resolve such concerns, attempts have been made to develop X-ray diagnostic equipment which automatically adjusts to give the appropriate technique. Automatic techniques using video brightness to achieve the appropriate dose have been tried with limited success. Such attempts generally have difficulty in accurately determining the proper dose in instances where there is raw X-ray in the image. Raw X-rays are those which have not been attenuated by passing through the patient's anatomy. An image of a body part, such as a hand, will contain, for example, attenuated X-rays, those passing through the palm and fingers, as well as unattenuated X-rays. The unattenuated X-rays pass between the fingers or about the outside edges of the hand. Because the desired amount of X-rays is only the dose necessary to penetrate the hand (or other portion of anatomy), the raw, unattenuated X-rays prevent an accurate determination of the proper dose.
Because the density of the tissue being X-rayed has a substantial effect on the attenuation of the X-rays, it is difficult to simply compensate for the particular portion of the anatomy which is being imaged. When imaging a substantial body part, such as a knee, the differences between the attenuated and unattenuated X-rays can be extreme. In such situations, the traditional automatic exposure control systems do not perform well. The traditional automatic system may result in insufficient technique, thereby resulting in an unclear image. In the alternative, the tradition automatic system may result in an excessive technique which is not only sufficient to form the image, but which subjects the patient to a much higher dose of radiation than is necessary.
The problem of exposure levels is particularly important in small C-arms, commonly referred to as "mini" C-arms, which have a opening of about 21 inches or less. The mini C-arms are often used to image extremities, such as hands, feet, knees and the like. Often, the mini C-arms are used in emergency rooms and other similar environments. Because of this, the mini C-arm is often moved from viewing one body part to another within a short period of time.
Those skilled in the art will appreciate that the exposure control systems on the mini C-arms tends to adjust with only moderate success. Thus, many patients are exposed to higher amounts of radiation than is necessary.
Thus there is a need for an improved automatic X-ray exposure control system which enables medical personnel or the system itself to control the X-ray diagnostic equipment to emit an X-ray dose which is sufficient to develop a clear image of the selected body part, while simultaneously keeping the radiation exposure to the patient at a minimum. Such a system desirably would compensate for widely varying anatomy and imaging requirements and be usable with conventional X-ray diagnostic equipment. Such a system would also be useable with mini C-arms.